Surveying Mine Shafts - Modern Inertial Measurement Methods

Transcription

1 Surveying Mine Shafts - Modern Inertial Measurement Methods Dr. Paul Althaus, Norbert Benecke, Uwe Kalz, Dr. Jörg Niese and Volker Schultheiß (all DMT GmbH & Co. KG, Germany) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 1

2 How save is you shaft? Some remarks on the importance of shafts in mining The world-wide demand for raw materials is increasing, also the prices Mining operations, esp. underground operations, are producing closely to their capacity limits 24 hours operability of the shafts is essential for the success of the mining operation But, often the shaft safety pillar is mined and this affects the shaft or parts of the shaft: In position (inclination, rotation, lateral movements, curves) In form (compression, deformation) In function The shaft hoisting installations move out of regular position Safety risks The hoisting speed of the cages must be reduced Production losses Production breakdown Danger to life or physical condition of workers IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 2

3 How save is you shaft? Accident can happen Mine rescue complete Mon Nov 19, 2007 All of the 27 miners who were trapped in a collapsed shaft at an Australian gold mine have now been brought to the surface Source: ABC News Rescue underway: Lihir says the 27 workers are being winched out of the mine by crane (Source: Reuters - Mike Hutchings) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 3

4 What has to be done? Regular shaft inspections are necessary Often the determination of spatial changes of the shaft column as well as any local anomalies have to be measured Traditional shaft survey is time- and cost-consuming (not popular with miners) Traditional shaft survey with plumbing laser beam, total station and polarized light method IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 4

5 What does the miner expect from survey? In ideal he would like a system in use with following features: Simple system mounting to the hoist cage or skip No staff required (automatically working) No disturbance of normal shaft operation / no extra measuring time Online availability of results No measurement errors Costless No system ever will fulfill these expectations in total, but. I affirm that DMT s inertial measurement system is closest to the fulfilment worldwide To be demonstrated IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 5

6 How does ISSM work? Basics ISSM = Inertial Shaft Survey for Mining Inertial measurement systems measure the rotation of their own carrier unit in all three spatial axes as well as the rectilinear accelerations in all three axes. Essential parts of inertial measurement systems are: 3 acceleration sensors 3 rotational rate sensors (gyroscopes) whose measurement axes are orthogonal to each another Every change in the orientation of the carrier produces a gyroscope signal which, subsequent to making the Earth rotation rate correction, describes the amount of rotation of the acceleration vector away from the navigation coordinate system After the acceleration vector has been transformed to the navigation coordinate system it is necessary to differentiate between the (required) acceleration and the disturbing affects of gravity as well as centripetal and Coriolis acceleration The reason for this is that the acceleration sensors should detect only movements in relation to the inertial space (in this case the centre of the Earth) In the next step the integration over time of the (required) acceleration yields the speed of the carrier in navigation coordinates The integration of the speed then gives the distance covered and consequently the position of the carrier IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 6

7 How does ISSM work? Data evaluation Analogue signals of the sensors (x, y and z) => analoguedigital converter => Micro-processor Storage of measured data Control of the measurement sequence System tests Plausibility checks Transformation of measured acceleration values to an acceleration vector in the carrier-fixed coordinate system Start Position Transformation into an Earth-fixed coordinate system (usually north and east direction and towards centre of the Earth. Inertial raw data Correction Instrument Error Navigation formula ZUPT, Kalman-Filter 3D-Trajektory Additional Data IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 7

8 How does ISSM work? System Configuration Sensors Batteries Processor A/D - Converter Technical Data: Diameter: Length: Weight: Ex proof: 195 mm 850 mm ca. 55 kg pressure tight and flame proof IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 8

9 How does it work? Accuracy and Reliability Inertia sensors have a specific error behaviour (drift in dependency to time) West [mm] 0 East -250 North r [mm] 500 South DMT has developed and implemented to ISSM high-precision calibration methods for compensation Achievable accuracy: horizontal ± 50mm/1000m vertical ± 100mm/1000m Depth [ m] IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 9

10 How does it work? Example from practice - Mounting Shaft survey with the inertial measurement unit ISSM in an Australian mine Assembly unit screwed onto two mounting brackets, secured on the pair of rails in the hoist cage Adjustment of mounting for different track widths as well as different rail thicknesses is possible Geodetic measurement of the mounting position of ISSM IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 10

11 How does it work? Example from practice - Mounting In the case of skip hoisting the assembly unit is suspended in a special construction underneath the skip IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 11

12 How does it work? Example from practice Initialization and Calibration At first the system has to be initialized (picture) All following measurement stages are performed automatically Calibration measurement while the hoist cage is resting (60 seconds) Calibration measurement means that the inertial measurement system determines its orientation to north (horizontal direction) and its inclination angle (vertical direction) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 12

13 How does it work? Example from practice - Measurement Alternating measurements Running periods Standstill periods Running periods Approx. 5 sec. to accelerate to the ideal speed of 4 m/s (up to 8 m/s is possible) 20 sec. of running time with ideal speed Approx. 5 sec. to brake to standstill Standstill periods 60 sec. necessary for carrying out the zero velocity update (ZUPT) By applying this method the sensor drift that inevitably occurs during each period of movement is mathematically minimised IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 13

14 How does it work? Example from practice - Measurement Continuous succession of running periods and standstill periods for entire length of the shaft down to the bottom Repetition of the measurements: typically 5 to 6 times Finally repetition of the calibration measurements and second geodetic measurement of the position All measurements are controlled and monitored from the machine room IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 14

15 How does it work? Example from practice Data recording All data recorded are saved on a PC card fitted inside the main assembly External terminal with optical infrared interface is connected for data transmission IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 15

16 What are the results? Evaluation and interpretation of the measured data in post-processing Draft results after some hours Final results and report within 2 weeks Data evaluation steps Scaling of the X,Y and Z acceleration values or gyroscope values in physical units Transformation of the acceleration values into the navigation coordinate -system with subsequent integration yields the speed in the X,Y and Z (flawed by the sensor drift) Determination of the speed correction value using the zero velocity update (ZUPT) and subsequent polynomial adjustment Correction of the speed by subtracting the correction value in all three directions Integration of the polynomial corrected speed yields the X,Y and Z distance covered by the hoist cage Elimination of the sections in the update phases enables the true movement profile of the hoist cage to be determined with reference to time Visualisation of the results as a north-south cross-section (or X coordinate) and east-west cross-section or (Y-coordinate) with reference to the depth or (Z coordinate). high resolution cross-section diagrams of the shaft. available in various data formats for inclusion in CAD programs or databases IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 16

17 How long does it take? Typical time schedule (1 cage) Mounting 30 min Initialization and Calibration 2 min Alternating measurements (5 to 6 times; 4 m/s) 1,000 m depth 180 min 2,000 m depth 360 min Final calibration 2 min Demounting 20 min Total time approx. 240 to 420 min (4 to 7 h) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 17

18 What are the costs? Typical costs (1 cage; 1,000 m depth) Measurement: 8,000 to 10,000 (depending on local conditions, e.g. mounting situation, speed) Data evaluation: 3,000 Mob / demob: depending on the location, can be shared by several measurements e.g. 6,000 to 8,000 for South Africa IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 18

19 What are the future challenges? ISSM system is highly operational Fast Accurate and reliable Cost-effective Results are limited to the spatial position of the cage No visualisation/measurement data of shaft walls and equipment, especially of critical or damaged areas Will it be possible to combine ISSM with an as-built-documentation-tool? Yes, it is possible! IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 19

20 What are the future challenges? Case study Shaft Lohberg 1 Laserscanner ( Stop & Go ) Geodetic Measurement Inertial Measurement IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 20

21 What are the future challenges? Case study Laser scanning in stop-and-go mode Front View Side View IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 21

22 What are the future challenges? Case study Laser scanning in stop-and-go mode IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 22

23 What are the future challenges? Case study Laser scanning in stop-and-go mode IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 23

24 What are the future challenges? Case study Laser scanning in stop-and-go mode Coordinate reference points and brackets IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 24

25 What are the future challenges? Case study Laser scanning in stop-and-go mode Shaft wall details - Measurements IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 25

26 What are the future challenges? Case study Laser scanning in stop-and-go mode Unwrapped Scan data IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 26

27 What are the future challenges? Case study Laser scanning in stop-and-go mode Deformation analysis (Comparison to cylinder) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 27

28 What are the future challenges? Case study Laser scanning in kinematic mode IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 28

29 What are the future challenges? Development of a 2D-Scanner Advantages Measurement time (and costs) will be minimized (from some days to less a shift) System will measure self-sufficient System will be applicable for small diameter shafts (or cavity entrances) System will be applicable for shafts without any cage or skip Challenges Correlation of track and time (by combination with ISSM system) High-level-explosion-proofness (requirement by customers from underground coal mining) IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 29

30 What are the future challenges? Development of a 2D-Scanner Wireline (logging cable) Tool body with double protection: pressurized apparatus p plus flameproof enclosure d and intrinsic safety ib flameproof enclosure d Spacious separated laser generator and prism drive (special care has to be taken of the drive shaft feed through) Optical or ultrasonic collision detection with data link to the surface winch unit Internal power supply or supply via logging cable with special cable/ insulation monitoring Measurement of all movements by an inertial measurement unit (ISSM) and active gyro stabilisation Proposed Carrier System Diameter: ~ 300 mm Weight: ~ 200 kg Height: ~ 2 m Cablehead Power supply (accumulator) Flameproof enclosure+ Pressurized apparatus Inertial mesurement unit (ISSM) and gyroscopic stabilizer Scanner-electronics laser window Mounting rods Rotating prism Drive shaft Feed through Prism drive (ib) Flameproof enclosure+ Intrinsic safety ib Collision detector IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 30

31 What are the future challenges? Development of a 2D-Scanner Other components Winch, Lock & Return Pulley Requirements Speed min. 1 meter/second Cable length min. 1,000 m... Development of System Control Hard- / Software IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 31

32 What are the future challenges? Development of a 2D-Scanner Availability? Wireline (logging cable) End of 2009 Cablehead Power supply (accumulator) Flameproof enclosure+ Pressurized apparatus Inertial mesurement unit (ISSM) and gyroscopic stabilizer Scanner-electronics laser window Mounting rods Rotating prism Drive shaft Feed through Prism drive (ib) Flameproof enclosure+ Intrinsic safety ib IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 32 Collision detector

33 Thank you for your attention! Glückauf! Contact: DMT GmbH & Co. KG Exploration & Geosurvey Norbert Benecke Am Technologiepark Essen Telefon +49 (0) Fax +49 (0) Norbert.Benecke@dmt.de Internet IMSCON 2008 July 23 rd -25 th, 2008 South Africa Page 33